package priv.pront.code.national.acwing.base;

import java.util.Scanner;

public class P1928_外星密码 {

    static StringBuilder sb = new StringBuilder();
    public static void main(String[] args){
        Scanner scanner=  new Scanner(System.in);
        String s = scanner.next();
        f(s);
        System.out.println(sb.toString());
    }


    private static StringBuilder f(String s){
        if(s.contains("[") && s.contains("]")){
            return new StringBuilder(s);
        }
        return null;
    }
}
